For many summer means fireworks and sparklers - here are my quick tips(with video) on capturing cool photos using sparklers or really any small light source.
First task is to do this all safely. Don't hurt anyone in an effort to get a photo and make sure you are complying with all fireworks and sparkler laws in your area - beautiful photos can be made with glow sticks, flash lights and other non-dangerous light sources.
Your shutter speeds are going to range from 2 seconds on up to Bulb mode so the use of a tripod is a must.
Setup your camera - manual mode (M), a good starting point is a 5 second shutter speed, ISO 200 and an aperture around f/4.5.
Have your subject stand still and hold up a small light source so you can focus on them, either auto focus or manual, zoom in. After you get focus switch to manual so that the camera isn't struggling to get focus in the dark. You can also use back button focus to avoid this issue. They can now put away the little flash light
Once you have focus have them light the sparkler and start moving it around. Use the remote release to trigger the shutter or gently press the shutter button on the camera (you really need to be careful not to wiggle the camera when you press the button, alternatively you can use the self-timer: 2-sec delay but that does require a bit more coordination with your subject.
A third option is to use the remote shutter release and BULB mode in your camera. In the T4i/T5i bulb mode is activated by setting the camera to M and increasing the shutter speed past 30 seconds. This doesn't mean the shutter has to be longer than 30 seconds for your exposures, it will just stay open as long as you hold the shutter release button down. This is great if someone is trying to write their name with a sparkler, you hold it down just as long as it takes the subject, when you release the button the shutter closes. With sparklers I notice that the slower you move them the more sparky trails you get - fast moving sparklers leave a more smooth line of light. You are limited by your imagination!
Video: Sparkler Photos - Long Exposure Light Painting
Related Video - How To Photograph Fireworks